The present invention relates to compositions for and methods of reducing low density lipoprotein cholesterol and total cholesterol concentrations in the blood. In particular, the present invention relates to compositions containing plant sterols, soy protein, and isoflavones, and combinations thereof, which are useful for lowering LDL-cholesterol and total cholesterol blood concentrations and for preventing or minimizing development of atherosclerosis.
Cardiovascular disease is a leading cause of morbidity and mortality, particularly in the United States and in Western European countries. Several causative factors are implicated in the development of cardiovascular disease including hereditary predisposition to the disease, gender, lifestyle factors such as smoking and diet, age, hypertension, and hyperlipidemia, including hypercholesteremia. Several of these factors, particularly hyperlipidemia and hypercholesteremia, contribute to the development of atherosclerosis, a primary cause of vascular and heart disease.
High blood cholesterol concentration is one of the major risk factors for vascular disease and coronary heart disease in humans. Elevated low density lipoprotein cholesterol (hereafter xe2x80x9cLDL-cholesterolxe2x80x9d) and elevated total cholesterol are directly related to an increased risk of coronary heart disease. Cholesterol and Mortality: 30 Years of Follow-Up from the Framingham Study, Anderson, Castelli, and Levy, JAMA, Vol 257, pp. 2176-80 (1987).
Ingestion of soy protein materials in the diet is associated with a lower risk of coronary heart disease, which may reflect decreases in serum cholesterol levels. Soy protein materials are known to reduce total cholesterol and LDL-cholesterol levels in the blood of animals. A recent meta-analysis of the effects of soy protein intake on serum lipids in humans has shown that dietary soy protein is significantly related to lowering serum concentrations of total cholesterol and LDL-cholesterol in humans. Meta-Analysis of the Effects of Soy Protein Intake on Serum Lipids, Anderson, Johnstone, and Cook-Newell, N. Engl. J. Med., Vol. 333, No. 5, pp. 276-82 (1995).
Ingestion of phytosterols, compounds which are found in whole soybeans, has also been shown to reduce the circulating total and LDL cholesterol levels in the blood. Dietary Phytosterols: A Review of Metabolism, Benefits, and Side Effects, Ling and Jones, Life Sci., Vol. 57:3, pp. 195-206 (1995). Phytosterols are sterol compounds produced by plants which are structurally very similar to cholesterol except that they always contain some substitutions at the C24 position on the sterol side chain. Common plant sterols include the unsaturated sterols xcex2-sitosterol, campesterol, and stigmasterol, which are shown in FIG. 1, and their saturated counterparts sitostanol and campestanol, shown in FIG. 2. Dietary sources of phytosterols are corn oil, soybean oil, and other plant oils which contain the relatively hydrophobic compounds.
The phytoestrogenic isoflavones, shown in FIGS. 3 and 4, are another set of compounds that are found in whole soybeans which have recently been recognized as a significant factor in reducing LDL and total cholesterol concentrations in the blood. Purified concentrated isoflavones, particularly genistein, suppress the biosynthesis of cholesterol as well as prevent the oxidation of LDL cholesterol, an important step in the development of atherosclerosis. See e.g., Korean Patent No. 97-20103; Oxidized Low Density Lipoprotein-Mediated Activation of Phospholipase D in Smooth Muscle Cells: a Possible Role in Cell Proliferation and Atherogenesis, Natarajan et al., J. Lipid Res. 36:9 pp. 2005 -16 (September 1995).
In the conventional processing of whole soybeans to produce soy oils, soy protein, and pharmaceutical or dietary supplement compositions, the phytosterols, isoflavones, and soy protein are separated. The plant sterols are separated from soy protein and the isoflavones into a soy oil fraction which contains fats and fat solubles by mechanical or chemical extraction of dehulled soybeans, The soy oil fraction is separated from the remaining soy materialsxe2x80x94the xe2x80x9cdefatted soy materialxe2x80x9dxe2x80x94for use in soy and vegetable oils, which may be further processed to form shortenings, margarines, and lecithin.
The defatted soy materials, usually defatted soy flakes, are used as a starting material to produce products containing substantial amounts of soy protein such as soy protein concentrates and soy protein isolates. The defatted soy materials used to produce soy protein products also contain the isoflavones. However, in conventional processes for the production of soy protein materials such as soy protein concentrates and soy protein isolates, substantial amounts of the isoflavones are separated from the soy protein material by washing the soy protein material with an alcohol extract or an aqueous extract. See, e.g., Soy Protein Products Characteristics, Nutritional Aspects and Utilization, pp. 3-6 (Pub. Soy Protein Council, 1987).
In the commercial production of soy protein materials the focus has been to separate the isoflavones from the soy protein material since isoflavones have been associated with poor taste, odor, and/or color when present in a soy protein material. For example, U.S. Pat. No. 5,804,234 teaches a process for removing isoflavones from a soybean material by contacting the protein material with an adsorbent resin to produce a better tasting soybean protein. Alcohol extraction of soy protein materials is particularly preferred since alcohol extraction is purported to produce a better tasting vegetable protein material than aqueous extraction, in part because alcohol is quite effective in removing isoflavones from the soy protein material. See, e.g., Japanese Patent No. 63-245,648A.
Recent efforts have also been focused on separating the isoflavones from plant materials in which they occur, particularly soy beans and clover, to provide a purified isoflavone material which can be used to provide health benefits. For example, the following patents disclose various methods of separating isoflavones from plant materials: U.S. Pat. Nos. 4,428,876; 5,702,752; 5,679,806; 4,390,559; 4,366,248; 4,366,082; 4,264,509; 4,232,122; 4,157,984; Japanese Patent Nos. 1-258669A; 5-170756A; 41-90720A; 62-126186A; 62-126185A; and PCT Patent Application No. WO 93/23069. The separated isoflavone compounds may be used in pharmaceutical compositions or dietary supplement compositions to prevent or treat a variety of deleterious health conditions including lowering elevated cholesterol levels. For example, the separated isoflavone materials may be utilized in pharmaceutical or dietary supplement compositions as described in U.S. Pat. Nos. 5,516,528; 5,424,331; 5,569,459; 5,654,011 and PCT Patent Application No. WO 93/23069.
New methods and compositions utilizing soy components and which are capable of providing significant lowering of LDL and total cholesterol levels in the blood to significantly reduce the risk of atherosclerosis and coronary heart disease remain desirable.
In one aspect, the present invention is a composition containing a soy protein material containing at least 49% soy protein by dry weight of the soy protein material, at least one isoflavone selected from the group consisting of genistein, daidzein, glycitein, biochanin A, formononetin, and their respective naturally occurring glycosides and glycoside conjugates, and a plant sterol, where the plant sterol forms at least 0.49% of the composition by weight.
In another aspect, the present invention is a composition containing a soy protein material which contains at least 49% soy protein by dry weight of the soy protein material, and a plant sterol, where the plant sterol forms at least 0.49% of the composition by weight.
In a further aspect, the present invention is a composition containing at least one isoflavone selected from the group consisting of genistein, daidzein, glycitein, biochanin A, formononetin, and their respective naturally occurring glycosides and glycoside conjugates, and a plant sterol, where the plant sterol forms at least 0.49% of the composition by weight.
In yet another aspect, the present invention is a method for lowering the concentration of LDL and total cholesterol in the blood of a human in which a soy protein material containing at least 49% soy protein by dry weight of the soy protein material, an isoflavone selected from the group consisting of genistein, daidzein, glycitein, biochanin A, formononetin, and their respective naturally occurring glycosides and glycoside conjugates, and a plant sterol are co-administered to the human to decrease the concentration of LDL and total cholesterol in the blood of the human. The plant sterol is co-administered in an amount such that the plant sterol comprises at least 0.49% of the combined weight of the co-administered soy protein material, isoflavone, and plant sterol. In a preferred aspect, the plant sterol, soy protein material, and isoflavone are co-administered to the human to prevent or minimize the development of atherosclerosis in the human.
In still another aspect, the present invention is a method for lowering the concentration of low density lipoprotein cholesterol and total cholesterol in the blood of a human in which a soy protein material containing at least 49% soy protein by dry weight of the soy protein material and a plant sterol are co-administered to a human to decrease the concentration of LDL and total cholesterol in the blood of the human. The plant sterol is co-administered in an amount such that the plant sterol comprises at least 0.49% of the combined weight of the co-administered soy protein material and plant sterol. In a preferred aspect, the plant sterol and the soy protein material are co-administered to the human to prevent or minimize the development of atherosclerosis in the human.
In yet another aspect, the present invention is a method for lowering the concentration of low density lipoprotein cholesterol and total cholesterol in the blood of a human in which a plant sterol and an isoflavone selected from the group consisting of genistein, daidzein, glycitein, biochanin A, formononetin, and their respective naturally occurring glycosides and glycoside conjugates are co-administered to the human to decrease the concentration of LDL and total cholesterol in the blood of the human. The plant sterol is co-administered in an amount such that the plant sterol comprises at least 0.49% of the combined weight of the co-administered isoflavone and the plant sterol. In a preferred aspect, the plant sterol and the isoflavone are co-administered to the human to prevent or minimize the development of atherosclerosis in the human.
In a further aspect, the present invention is a composition containing a soy hypocotyl material and a plant sterol, where the plant sterol forms at least 0.49% of the composition by weight.